Ongoing surveillance studies consistent suggest that inhalants are the fourth most prevalently used psychoactive substance. Inhalants are unique among drugs of abuse because they are legal for all ages, easily accessible, and inexpensive. Moreover, the immediate medical consequences of inhalant use, including respiratory problems, damage to the liver, heart, or brain, and even death, can be much more severe than the more prevalently used substances: tobacco, alcohol, and marijuana. Surveillance data indicate that inhalants generally are first used at a young age (consistently nearly 20% of 8th graders surveyed in the Monitoring the Future study report having used inhalants), suggesting that inhalant use may play a developmental role in use of other substances such as cocaine or opiates. Relative to other substances, however, very little is known about inhalant use and even less is known about inhalant abuse and dependence. Such data are critical to a relevant public health response and prevention efforts directed at inhalant misuse. For illustration, although a withdrawal syndrome for inhalants is absent from the DSM-IV, preliminary data collected in our laboratory suggest that inhalant withdrawal is experienced by some inhalant users. We propose to develop Substance Abuse Module (SAM) questions specifically for the different types of inhalants (solvents, aerosols, gases, and nitrites) and to quantitatively estimate the psychometrics of a general inhalants category of abuse and dependence diagnoses, preliminarily study separate diagnoses for the different types of inhalants, investigate the occurrence of inhalant use-related abuse and dependence among users of inhalants, qualitatively explore the experiences of inhalant users relevant to their inhalant use (e.g., how did they learn about inhalants, did their inhalant use lead to trying other drugs), and to explore qualitatively parents' and health care professionals' knowledge of inhalants, consequences of use, and efforts to warn children of this danger. We also will study the comorbidity and age-of-onset of other substance use-related disorders among inhalant users. We proposed to address these issues by reanalyzing the WHO/NIDA/NIAAA Reliability and Validity of Substance Use Disorders data, conducting focus groups, and conducting a test-retest-validity study of abuse and dependence disorders in older adolescent and young adult inhalant users with questions regarding specific types of inhalants.